Experimental study of nonequilibrium fluctuations during free diffusion in nanocolloids using microscopic techniques

Area of Science:

• Colloid science
• Soft matter physics
• Nanotechnology

Background:

• Concentration fluctuations are crucial for understanding colloidal systems.
• Small-angle light scattering (SALS) is a powerful technique for studying these dynamics.
• Previous studies have explored various aspects of colloidal behavior, but distinct behaviors in different nanoparticle types warrant further investigation.

Purpose of the Study:

• To quantitatively investigate concentration fluctuations in colloidal systems using a novel SALS setup.
• To compare the dynamic behavior of gold and silica nanoparticles of different sizes.
• To elucidate the factors influencing correlation time in early-stage fluctuations.

Main Methods:

• Utilized a small-angle light-scattering setup combined with a shadowgraph technique.
• Employed a CCD camera with an objective for an enhanced field of view.
• Conducted experiments with 20 nm gold and 200 nm silica colloids.
• Analyzed structure factors and correlation times, alongside qualitative temporal evolution using recursive plots and spatial-temporal sections.

Main Results:

• Extracted structure factors and correlation times for both gold and silica colloids.
• Observed a concave correlation time versus wavenumber relationship for gold nanocolloids.
• Observed a convex correlation time versus wavenumber relationship for silica colloids.

Conclusions:

• The distinct correlation time behaviors are attributed to particle size and potential plasmonic interactions in gold colloids.
• This study provides quantitative insights into the dynamics of different nanoparticle systems.
• The findings contribute to a deeper understanding of colloidal dynamics and interactions.